It has become fashionable to glaze office buildings with window assemblies comprising glass sheets arranged in a rectangular grid pattern and bordering fairly close to one another without any major surface interruption--i.e. without any retainer device overlapping adjacent panes that protrudes outward beyond the outer glass surface. Such flush mounting of windows presents to the external viewer the appearance of a continuous plane surface.
Where only one lite of glass is involved, the problem of retaining the glass in place is not too severe, since there is ample opportunity to adhere the single pane to the grid frame or mullion using a strong adhesive bond. When dual-pane insulated glass is involved, both the inboard lite and outboard lite must be adhesively bonded; conventionally, there is no mechanical retaining element present. Conventional arrangements often do not permit the outboard lite of glass to be as firmly anchored by the bonding cement or agent as would be wished, since there is limited bonding surface available and shear stresses are severe. A further difficulty is that with many conventional arrangements, the bonding cement has to be applied in the field where rain, dust, grease, etc., interfere with provision of clean glass and metal surfaces to which the bonding cement can adhere; furthermore, adverse temperature conditions and inadequacies of field labour may contribute to less than an adequate bond.
Various solutions to this problem have been proposed by prior inventors.
These various prior solutions tend to be lacking in at least one of the following respects:
(a) The structure does not lend itself to pre-fabrication of the window assembly but requires application of bonding material in the field. PA1 (b) The structure admits of limited bonding surface, especially for the outboard lite. PA1 (c) The structure does not permit the use of the conventional insulated dual-pane assembly comprising an inboard and outboard lite separated by a peripheral spacer and having primary and secondary seals. PA1 (d) The structure does not admit of quick and secure positioning thereof (at least along one edge) to the mullion. PA1 (e) The structure applies or transmits stresses in the connection of one window panel to the adjoining window panel. PA1 (f) The structure does not permit ready removal of individual panels for repair or replacement.
Of the prior solutions, some of those of Francis superficially somewhat resemble the structure of the present invention (see U.S. Pat. Nos. 4,500,572 and 4,552,790). Francis, however, does not provide in two opposed integral extrusions (respectively one for each of the two opposed sides of the window assembly) a gripping means for the inboard lite and a push-on attachment/positioning means for quick attachment of one side of the window assembly. Furthermore, Francis departs in a number of his solutions from the conventional dual-pane insulated window structure having a peripheral spacer and two seals and instead varies this structure, depending upon which of his various alternative solutions is adopted. Francis instead permanently fastens two adjacent window panels using a fastener common to both. This means that stresses applied to one window panel can be undesirably transmitted to the next adjoining panel via the common fastener. Further, one window unit cannot be removed without unfastening adjacent window units.